Washington CNN  — 

Georgia Republican Sen. Johnny Isakson announced on Wednesday that he will resign at the end of the year, citing health concerns.

Isakson, the chairman of the Senate’s Ethics and Veterans’ Affairs committees, will leave after decades in elected office, claiming the distinction as the only Georgian ever elected to the state House, state Senate, US House and US Senate.

In a statement, Isakson said he had surgery to remove a growth on his kidney this week and was still recovering from a fall in July that fractured four ribs, all while his Parkinson’s disease continued to progress.

“I am leaving a job I love because my health challenges are taking their toll on me, my family and my staff,” said Isakson. “With the mounting health challenges I am facing, I have concluded that I will not be able to do the job over the long term in the manner the citizens of Georgia deserve. It goes against every fiber of my being to leave in the middle of my Senate term, but I know it’s the right thing to do on behalf of my state.”

Senate Majority Leader Mitch McConnell praised Isakson as a “first-rate legislator” and a “man of the highest integrity,” while Senate Democratic leader Chuck Schumer called Isakson “one of the kindest, most thoughtful senators.”

“Independent of any party or politics, everyone will miss Johnny,” Schumer said.

Republican governor can appoint replacement before special election

The new vacancy will reinforce the perception that Georgia is one of the most important battlegrounds in the 2020 election.

The state will have two Senate seats on the ballot. Republican Gov. Brian Kemp will appoint a replacement for Isakson until a special election held in November 2020 will determine who will fill the remainder of his term – the same time Republican Sen. David Perdue is up for reelection. Isakson’s seat will be up for a full, six-year term in 2022.

Some Democrats also hope to make Georgia, where Donald Trump bested Hillary Clinton by just 5 percentage points in 2016 and the GOP won an even closer governor’s race last year – as well as fellow Sun Belt states Arizona and Texas, which have also moved rapidly leftward in recent years – competitive in the presidential race.

The top Democratic prospect for the Senate race would have been Stacey Abrams, the former state House Democratic leader who became a national star during her narrow loss in last year’s governor’s race.

But Abrams declined to challenge Perdue, opting to launch a group focused on fighting voter suppression, and passed on running for Isakson’s seat after his resignation announcement.

The Atlanta Journal-Constitution reported that Kemp’s potential appointments include Georgia Attorney General Chris Carr, state Senator Butch Miller, Lt. Gov. Geoff Duncan, Rep. Doug Collins and Agriculture Secretary Sonny Perdue.

Nick Ayers, vice President Mike Pence’s former chief of staff, was another potential candidate for the shortlist, but said he would not be appointed. Ayers played an instrumental role in getting Pence to Georgia to campaign for Kemp in 2018.

Ayers was offered, but turned down, the White House chief of staff role because President Donald Trump wouldn’t agree to his time limits. Ayers only wanted to stay on the job for a few months because he knew there was a possibility the Senate seat could become open, according to a source familiar with the discussions.

“I’ve enjoyed being involved in every election cycle since 2002 fighting for the policies and the people I believed in. My decision to leave the White House and Washington, D.C. earlier this year was for the sole purpose of stepping back from politics and enjoying this season of life with my wife and three young children. They are the priority now and for the many years to come. Governor Kemp has a number of great options to choose from who will represent our state with success and distinction – but I won’t be one of them,” Ayers said in a statement.

CNN’s Adam Levy contributed to this report.